Polyvinyl chloride films applied to agricultural or horticultural vinyl houses ere used for a fixed period, and then replaced with a new one because of the deterioration of optical transmission or serviceability with age or by dust adhesion.
As a result, used polyvinyl chloride films arise, and it is necessary to dispose of them with a certain method. If the used films are beat-treated with an ordinary refuse incinerator under the air (oxygen) atmosphere, the incineration temperature rises higher with the generation of noxious gases, such as a hydrogen chloride gas and dioxins (popularly known as chlorodibenzoxines), and of a malodor, so that the refuse incinerator will be damaged, or pollutions will be caused. Therefore, the heat treatment is seldom practiced.
Another methods including a method for extracting the oils from polyvinyl chloride to be salvaged, or for throwing the used films into reclaimed land without any treatment; the former, however, causes problems with salvage costs and efficiency, the latter makes the land loose and destroy the natural circulating system; therefore, these are not excellent methods.
Thus, it is suggested that the waste plastic materials including chloric polymer compounds, such as polyvinyl chloride, should be treated making generated gases, such as hydrogen chloride gases, harmless. In Japanese Provisional Publication No. 3040 of 1988, for example, a fusing-setting method was provided for heating and fusing waste plastic materials at pyrolysis temperature of at least 150.degree. C. or more with crushing and kneading, while calcium salts were introduced, so that the harmful hydrogen chloride gases generated would be harmless by the salts. This method conducted under the air atmosphere (oxygen), however, has a potential for generating harmful materials to the human body and a danger to ignition. Moreover, this method needs to dispose of the solid waste plastic materials.